This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Bacterial meningitis still remains significant despite advances in antimicrobial chemotherapy and supportive care. It is mainly due to an incomplete understanding of the pathogenesis of this disease. Escherichia coli K1 is the major cause of neonatal Gram-negative bacterial meningitis and its invasion of human brain microvascular endothelial cells (HBMEC) is a prerequisite for its penetration of blood-brain barrier (BBB) in vivo. We have previously reported that cytotoxic necrotizing factor-1 is the major bacterial determinant responsible for bacterial invasion of HBMEC, constituting the BBB. However, its deletion reduces bacterial ability to invade into HBMEC by only 50%, suggesting that there must be other bacterial determinant(s) responsible for E. coli K1 invasion of HBMEC. We have recently identified and characterized a novel virulence factor called HEK (Hemagglutinin in E. coli K1). Our preliminary results demonstrated that the hek gene located in an RS218-speciifc island contributes bacterial adhesion and invasion of HMBEC through signaling pathways different from CNF1. In addition, expression of HEK only is sufficient to allow the non-invasive E. coli K12 strain invasive. Therefore, we hypothesize that HEK is another major invasion factor involved in E. coli K1 invasion of HBMEC. Two specific aims are proposed: [1] To determine mechanism of HEK-mediated E. coli invasion of HBMEC and [2] To confirm the role of HEK in E. coli meningitis. Overall, the information derived from this proposal should enhance our understanding of the pathogenesis of E. coli meningitis and potentially lead to the development of novel strategies to prevent E. coli meningitis.